Energy absorber for vehicles

ABSTRACT

This energy absorber incorporates a mounting bracket secured to a vehicle which by track and follower mechanism slidably mounts a support bracket that is secured to a vehicle bumper. One bracket supports a laterally extending energy absorbing band of resilient material engaged by the follower carried by the other bracket. On impact, the brackets are telescoped inwardly and an intermediate portion of the band is displaced by the follower to effect band deflection and energy absorption. On rebound, the band gradually restores to its original configuration to return the brackets and bumper to its pre-impact position.

This invention relates to energy absorbers and more particularly to anenergy absorbing unit featuring new and improved energy absorbingresilient band and mounting bracket construction yieldably couplingrelatively movable vehicle components.

Prior to the present invention, a wide variety of energy absorber unitshave been utilized to mount a rigid, transversely extending bumper beamto the frame or unibody construction of a vehicle for absorbing impactenergy. Some of these units comprise telescoping inner and outercylinders or similar components which are movable from an extendedposition to a telescoped and collapsed position on bumper impact ofpredetermined magnitudes. These energy absorber units often employviscous fluids, spring devices or stretchable bands for dissipating theenergy of such impacts. While these energy absorber devices haveadequately performed to absorb impact energy, they are often complex inconstruction and have added considerable weight to the vehicle.

The present invention is drawn to a new and improved light-weight energyabsorbing unit having a minimal number of parts which comprises a pairof brackets that are telescopically movable relative to each other onimpact of the bumper of a vehicle. The brackets are slidablyinterconnected by a pair of pins or other follower mechanisms guided bytrack means. One of the brackets carries an endless band or belt oforiented plastic material which can be tailored to suit the variousenergy absorbing requirements by increasing or decreasing the thicknessof the band or, in the case of a multi-wrapped band, by varying thenumber of wraps of the material forming the band. The band is supportedin a laterally extending manner at either end by fixed pin means or byspecial pin means which can be cammed outwardly on impact of the bumperto deflect the band to effect absorption of impact energy. Followermeans guided by a track formed in one of the brackets will flex the bandin response to impact loads above a minimum load applied to the bumper.With the followr stretching the laterally-extending band from itsmidportion, there is increased band flexure in a foreshortened energyabsorbing unit.

It is a feature, object and advantage of this invention to provide a newand improved energy absorbing unit, which is particularly adaptable forvehicle bumpers, vehicle suspensions or the like, that incorporates aminimal number of components which is light-weight and highly effectivein absorbing input energy on the displacement of a resilientlaterally-extending energy absorbing band. After removal of the impactload, the band will slowly return to its original position so that thebumper or other component will be returned to its original positionwithout excessive rebound velocity.

It is another feature, object and advantage of this invention to providean energy absorbing unit incorporating a pair of relatively movabletelescopic brackets connecting a bumper to a vehicle which incorporatesa slidable follower guided by a longitudinally extending track. Onbumper impact, the follower stretches a laterally extending resilientband in response to an impact load applied to the bumper to dissipateimpact energy. The force of the recovery of the band returns the bumperassembly and the brackets to their pre-impact position. The band ispreloaded and yieldably holds the bumper outwardly of the vehicle body.

It is another feature, object and advantage of this invention to providea new and improved energy absorbing unit comprising a laterallyextending band of resilient material which is supported at its ends andwhich is stretched by a follower mechanism to an extended position toeffectively absorb input energy.

These and other features, objects and advantages of this invention willbe more apparent from the following detailed description and drawings inwhich:

FIG. 1 is a perspective view of an automotive vehicle chassis frame anda pair of energy absorber units mounting a bumper assembly to the frame;

FIG. 2 is an enlarged sectional view taken along the plane indicated byline 2--2 of FIG. 1 showing an energy absorber unit of this invention inits normal extended position;

FIG. 3 is a view taken along the plane indicated by line 3--3 of FIG. 2;

FIG. 4 is a view similar to the view of FIG. 3 but illustrating amodification of the invention;

FIG. 5 is a view taken generally along the plane indicated by line 5--5of FIG. 4;

FIG. 6 is another view similar to the view of FIG. 3 showing a secondmodification of the invention; and

FIG. 7 is a view taken generally along the plane indicated by line 7--7of FIG. 6.

Referring now to FIG. 1 of the drawings, there is shown a portion of avehicle chassis frame 10 comprising a pair of laterally spaced siderails 12 having forwardly extending front portions 14 interconnected bya cross member 16. Secured by bolts or other suitable fasteners to theend of the front portions 14 of the frame are a pair of energy absorbingunits 18 and 20 that support a bumper assembly 22 outwardly of the bodywork 24 of the vehicle. Since both of the units are the same inconstruction, only one is described in detail.

As shown, the energy absorbing unit18 has a U-shaped frame bracket 25opening outwardly from the body work with upper and lower legs 26 and 28interconnected by a base 30. The base 30 has openings 32 extendingtherethrough for reception of threaded fastener means 34 that secure thebracket 25 to the end of the front portion of the frame. The upper andlower legs 26 and 28 of the bracket 25 extend longitudinally from theend of the side rails. Mounted in the outer end portion of the legs ofbracket 25 are a pair of vertical slide pins 36 and 38 longitudinallyaligned with each other which are slidably guided in longitudinallyextending slots or tracks 42 and 44 formed respectively in the upper andlower sides 46 and 48 of a bumper bracket 50. The bumper bracket istelescopically mounted on the frame bracket. The two sides of the bumperbracket are vertically spaced from each other by an intermediate portion52 which is adapted to be secured to the bumper assembly 22 by threadedfasteners 54. The upper and lower sides of bumper bracket 50 are thesame, each having laterally extending wings notched at 56 and 58 on theouter extremities thereof to receive the static mounting pins 60 and 62around which a multi-layered energy absorbing band or belt 64 is looped.The band 64 is preferably a resilient energy absorbing unit of thinoriented plastic material such as that more fully described in U.S. Pat.No. 4,046,411 for "Energy Absorber and Method of Manufacture" which ishereby incorporated by reference.

As best shown in FIGS. 2 and 3, the energy absorbing band 64 ispreloaded and ready for immediate stretching and energy absorption onapplication of predetermined impact loads applied to bumper 22. Theinner length 66 of band 64, extending between pins 60 and 62, isstretched over the rear slide pin 36. In a similar manner, the outerlength 68 of belt 64 is stretched over the outer slide pin 38. With theenergy absorbing belt initially stretched and preloaded as bestillustrated in FIG. 3, the bumper assembly is yieldably held outward ofthe body work and is ready for inward stroking movement and effectiveenergy absorption in response to a predetermined impact load directed tothe bumper assembly.

In addition to the longitudinal guidance by pin 36 and 38 riding in theslots 42 in response to telescoping movement of the two brackets on thestroking of the bumper, the sides of the bumper bracket 50 are eachprovided with a strap, such as strap 70, which fits over the guides thelegs 26 and 28 of the frame bracket 25 on the telescoping movement ofthe brackets relative to each other. Thus, on application of an impactload to the bumper, the bumper will be moved inwardly relative to theframe member and the body work. The pins 36 and 38 will be guided in thetrack 42 to stretch both lengths 66 and 68 of the looped energy absorberband by equal amounts to effect the absorption of impact energy and thusprotect the vehicle body work from damage. On removal of the impactloads, the energy absorbing band will gradually return to its originalpreloaded position shown in FIG. 3. This action gradually moves the pins36 and 38 from a forward position in slot 42 to the position shown infull lines in FIG. 3 and the bumper is returned to its original positionat low velocity.

FIG. 4 illustrates another energy absorbing unit 80 forming a secondembodiment of the invention. In construction, this embodiment comprisesa U-shaped frame bracket 82 having upper and lowr legs 84 and 86vertically bent at their ends adapted to be secured to the front of thevehicle side rails 12 by threaded fasteners extending through openings87. The frame bracket is formed with a V-shaped nose portion 88interconnecting the legs which is adapted to contact a central portionof inner length 90 of an energy absorber band 92 which can be made froma single thickness of oriented plastic material instead of themulti-wrap material of the band of the first embodiment. The upper andlowr legs 82 and 86 are formed with elongated slots or tracks 94 and 96into which inwardly extending tangs 98 and 100 of upper and lower sides102 and 104 of bumper bracket 106 extend. These tangs form followerswhich ride in the tracks 94 and 96 as the bracket telescopes on bumperimpact to guide the relative movement of the bracket member on impact ofthe bumper. The bumper is secured to an outer base portion 108interconnecting sides 102 and 104 of the bumper bracket by suitablefasteners, not shown, extending through openings 109. The sides of thebrackets are wing-shaped and have tips which are notched at 112 and 114to receive the static pins 116 and 118 around which the band 92 iswrapped. As shown, the band 92 has an outer length 120 stretchingbetween the pins. The length 120 has a midportion which is in contactwith the projecting midportion of length 90 as illustrated in FIGS. 4and 5. As will be appreciated, the inner length 90 has a larger preloadthan the outer length 120 in view of the differences in preloadstretching. On impact, the nose portion of the bracket will stretch theband as the two brackets telescope relative to one another to absorbimpact energy. On removal of impact loads, the band gradually returns toits preload position to reposition the bumper assembly in its outerprotective position outwardly of the vehicle body. As in the previousembodiments, the return of the bumper to this position is controlled bythe rate of recovery of the band and materials are selected so that thereturn rate is sufficiently low for slow bumper recovery.

The modification of the invention shown in FIGS. 6 and 7 is somewhatsimilar in construction and operation to the previously describedmodification. FIGS. 6 and 7 illustrate an energy absorber unit 130having a frame bracket 132, U-shaped in cross section, which opensoutwardly with upper and lower sides 133 and 134. These sides areconnected by a base 136 that is formed with suitable openings 138 forreception of threaded fasteners which attach the frame bracket to theside rails. The outer end of the frame bracket 132 carries a pair ofvertical slide pins 140 and 142 which are guided in longitudinallyextending slots or tracks 144 and 146 formed in the upper and lowersides 148 and 150 of a U-shaped bumper bracket 152. The sides of thebumper bracket are interconnected at their outer ends by a base 154which is formed with openings 156 for threaded fasteners which secure abumper assembly, not shown, to the bumper bracket. As in the embodimentsof FIGS. 1-3, pins 140 and 142 engage the inner and outer lengths 160and 162 of an energy absorbing band 164 which is like that of theembodiment of FIGS. 4 and 5. The band 164 extends around laterallymovable pins 166 and 168 which are vertically mounted in laterallyspaced notches 174 and 176 formed in the sides of the bumper bracket. Inthe pre-stressed position, the pins 166 and 168 are held in thelaterally spaced notches 174 and 176. However, on impact greater than apredetermined minimal impact load on the bumper, camming ramps 180 and182 force the pins 166 and 168, anchoring the ends of the band,outwardly to increase the stretch of the energy absorbing band.

Thus, on impact of the bumper assembly, the pins 140 and 142 areactivated to effect a stretching of the energy absorbing band from itsmidportion, as the pins 166 and 168 stretch the band laterally to effectincreased stretching and energy absorption.

Accordingly, it will be appreciated that this displacement of the bandfrom its outer ends as well as the movement of the midportion of theband on impact will absorb a greater amount of impact energy as comparedto the FIG. 1 embodiment for the same stroke.

While this invention has been described in connection with vehiclebumpers, it could be readily employed for suspensions and other similaruses. It will be appreciated that various modifications and embodimentsof the construction can be made in view of this description and withoutdeparting from the disclosure or the scope of the following claims.

We claim:
 1. An energy absorbing unit for operatively mounting a bumperbeam to a vehicle comprising a support bracket secured to the vehicle, abumper beam bracket secured to the bumper beam and extending inwardlytherefrom into telescopic relationship with respect to said supportbracket, longitudinally extending track means on one of said brackets,follower means carried by the other of said brackets operatively mountedand guided by said track means for movement between first and secondlongitudinal telescopic positions, an energy absorber of resilientmaterial looped into an endless band with outer ends operativelyconnected by inner and outer lengths, said band having its majordimension formed by said lengths extending laterally of said brackets,laterally-spaced fastener means connecting said outer ends of saidenergy absorbing band to one of said brackets and preloading said band,band displacement means for said inner and outer lengths carried by oneof said brackets, said inner and outer lengths of said band havingmidportions disposed outwardly of said band displacement meansassociated therewith whereby said band is operatively engaged and saidinner and outer lengths are stretched by said band displacement means assaid follower means moves with respect to said track means in responseto impact of said bumper resulting in the relative telescopic movementof said brackets from said first toward said second position to therebydissipate impact energy.
 2. An energy absorbing unit for operativelymounting a bumper beam to a vehicle and outwardly of the body workthereof comprising a support bracket secured to the vehicle, a bumperbeam bracket secured to the bumper beam of a vehicle and extendinginwardly therefrom into telescopic relationship with respect to saidsupport bracket, longitudinally extending track means on one of saidbrackets, follower means carried by the other of said bracketsoperatively mounted and guided by said track means for movement betweenfirst and second longitudinal telescopic positions, band means ofresilient material extending laterally of said brackets, laterallyspaced retainer means for said band means secured to one of saidbrackets, said band means being looped about said retainer means to forma continuous member with separate inner and outer lengths initiallystretched against said follower means to preload said band means andyieldably hold said bumper outwardly of said body work, said lengths ofsaid band means having a midportion disposed outwardly of said followermeans whereby each of said lengths of said band means is furtherstretched by said follower means as said follower means is displacedalong said track means in response to impact of said bumper resulting inthe movement thereof and the relative telescopic movement of saidbrackets from said first toward said second position to therebydissipate impact energy.
 3. An energy absorbing unit for operativelymounting a bumper beam to a vehicle outwardly of the body work thereofcomprising a support bracket secured to the vehicle, a bumper beambracket secured to the bumper beam and extending inwardly therefrom,longitudinally extending track means on one of said brackets, followermeans carried by the other of said brackets operatively mounted andguided by said track means for movement between first and secondlongitudinal positions, contact means carried by one of said brackets,endless energy absorbing band means extending laterally of saidbrackets, having separate inner and outer lengths, each of said lengthshaving a central portion engaged by said contact means, said band meanshaving looped outer ends operatively connecting said inner and outerlengths, first and second anchor means laterally spaced from one anotherconnecting said looped outer ends of said energy absorbing band means toone of said brackets to preload said band means and thereby yieldablyhold said bumper beam outwardly of the body work of the vehicle, saidcentral portion of said lengths being displaced outwardly as saidcontact means is displaced along said track means in response to impactloads applied to said bumper means to deform said inner and outerlengths of said band means for impact energy absorption as said band isdeflected from the midportion thereof.
 4. An energy absorbing unit foroperatively mounting a bumper beam to a vehicle outwardly of the bodywork thereof comprising a support bracket secured to the vehicle, abumper beam bracket secured to the bumper beam of a vehicle andextending inwardly therefrom, longitudinally extending track means onone of said brackets, follower means carried by the other of saidbrackets operatively mounted and guided by said track means for movementbetween first and second longitudinal positions, endless energyabsorbing band means extending laterally of said brackets, said bandmeans describing a loop having separate inner and outer lengths, each ofsaid lengths having a central portion directly contacted by saidfollower means, said band means having outer ends interconnecting saidinner and outer lengths, fastener means connecting said outer ends ofsaid energy absorbing band means to one of said brackets to preload saidband means against the other of said brackets to thereby yieldably holdsaid bumper beam outwardly of the body work of the vehicle, said centralportion being diplaced outwardly by said follower means as said followermeans is displaced along said track means in response to impact loadsmoving said bumper beam toward said body work to deform said band meansfor impact energy absorption as said midportion of said band isdeflected.
 5. An energy absorbing unit for operatively mounting a bumperbeam to vehicle comprising a support bracket secured to the vehicle, abumper beam bracket secured to the bumper beam of a vehicle andextending inwardly therefrom, longitudinally extending track means onone of said brackets, follower means carried by the other of saidbrackets operatively mounted and guided by said track means for movementbetween first and second longitudinal positions along said track means,energy absorbing band means of resilient material looped into an endlessbelt extending laterally of said brackets and having a midportioncontacted by said follower means, fastener means laterally spaced fromone another connecting the outer loops of said energy absorber to one ofsaid brackets, and cam means carried by the other of said brackets formoving said fastener means laterally outwardly in response to impactloads applied to said bumper beams and stretching said band means forimpact energy absorption as said midportion of said band is deflected bysaid follower means.